我已经使用socketio创建了一个小的Flask webapp,它应该可视化一个brew控制器。硬件是Raspberry Pi,控制器部分(硬件绑定和数据收集)是在独立的后台线程中完成的,该线程在create_app
开始。我需要确保后台线程只开始一次(即使我创建了多个应用程序对象)。所以我使用BrewController.get_instance()
函数来实现某种单例模式。后台线程用Flask-Socketio启动两次
import os
import time
import threading
import arrow
from sqlitedict import SqliteDict
from flask import Flask
from flask_bootstrap import Bootstrap
from flask_socketio import SocketIO
from flaskext.lesscss import lesscss
from config import config
from .brewcontroller import BrewController
background_thread = threading.Thread()
# Flask Plugins
bootstrap = Bootstrap()
socketio = SocketIO()
brew_controller = BrewController.get_instance()
db = SqliteDict('process_data.sqlite', tablename='pd', autocommit=False)
db.setdefault('t', [])
db.setdefault('temp_sp', [])
db.setdefault('temp_ct', [])
db.setdefault('ht_pwr', [])
db.commit()
from . import events # noqa
def create_app(config_name=None):
app = Flask(__name__)
if config_name is None:
config_name = os.environ.get('PIBREW_CONFIG', 'development')
app.config.from_object(config[config_name])
# init flask plugins
lesscss(app)
bootstrap.init_app(app)
socketio.init_app(app)
# create blueprints
from .main import main as main_blueprint
app.register_blueprint(main_blueprint, url_prefix='/')
# init the brew controller and start the background task if none
# exists yet
print(brew_controller)
if not brew_controller.initialized:
brew_controller.init_app(app)
background_thread = threading.Thread(
target=process_controller,
args=[app.config['PROCESS_INTERVAL']],
daemon=True
)
print('controller started')
background_thread.start()
return app
def process_controller(interval):
while(1):
current_time = arrow.now()
brew_controller.process()
data = {
't': current_time.format('HH:mm:ss'),
'temp_sp': '{:.1f}'.format(brew_controller.temp_setpoint),
'temp_ct': '{:.1f}'.format(brew_controller.temp_current),
'ht_en': brew_controller.heater_enabled,
'mx_en': brew_controller.mixer_enabled,
'ht_pwr': '{:.1f}'.format(brew_controller.heater_power_pct),
'ht_on': brew_controller.heater_on,
}
x = db['t']
x.append(data['t'])
db['t'] = x
db['temp_sp'].append(data['temp_sp'])
db['temp_sp'] = db['temp_sp']
db['temp_ct'].append(data['temp_ct'])
db['temp_ct'] = db['temp_ct']
db['ht_pwr'].append(data['ht_pwr'])
db['ht_pwr'] = db['ht_pwr']
db.commit()
socketio.emit('update', data)
time.sleep(interval)
但是线程仍然开始两次,我甚至得到两个不同的BrewController实例。所以我最终得到了两倍于我的数据库和重复值的数据。
后,我打电话manage.py运行看起来像这样(我打印的brewcontroller实例,看看它们是不同的)输出:
<pibrew.brewcontroller.BrewController object at 0x105777208>
<pibrew.brewcontroller.BrewController object at 0x105777208>
controller started
* Restarting with stat
<pibrew.brewcontroller.BrewController object at 0x10ca04240>
<pibrew.brewcontroller.BrewController object at 0x10ca04240>
controller started
* Debugger is active!
* Debugger pin code: 121-481-821
(31213) wsgi starting up on http://0.0.0.0:5000
我发现通过设置use_reloader
说法,我可以抑制这个我manage.py为False。
@manager.command
def run():
app = create_app()
socketio.run(app, host='0.0.0.0', port=5000, use_reloader=False)
但是,首先这种双重启动的原因是什么。对我来说,似乎有两个创建的进程。有人可以解释发生了什么,以及防止这种情况的最佳方法是什么。
我喜欢使用'before_first_request'处理程序的想法。但是我仍然有点麻烦,因为我不知道该把它放在哪里。当我使用工厂函数'create_app'时,模块中没有可用的应用程序对象。我也无法注册蓝图。 – MrLeeh
您可以在蓝图上使用[before_app_first_request](http://flask.pocoo.org/docs/0.11/api/#flask.Blueprint.before_app_first_request)。 – Miguel